.\" Copyright (c) 2005 Tom Rhodes
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.\" from IEEE Std 1003.1, 2004 Edition, Standard for Information Technology --
.\" Portable Operating System Interface (POSIX), The Open Group Base
.\" Specifications Issue 6, Copyright (C) 2001-2004 by the Institute of
.\" Electrical and Electronics Engineers, Inc and The Open Group.  In the
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.\" $FreeBSD: src/lib/libc/stdlib/a64l.3,v 1.3 2006/09/30 10:29:43 ru Exp $
.\"
.Dd November 20, 2005
.Dt A64L 3
.Os
.Sh NAME
.Nm a64l ,
.Nm l64a ,
.Nm l64a_r
.Nd "convert between a long integer and a base-64 ASCII string"
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In stdlib.h
.Ft long
.Fn a64l "const char *s"
.Ft char *
.Fn l64a "long int l"
.Ft int
.Fn l64a_r "long int l" "char *buffer" "int buflen"
.Sh DESCRIPTION
These functions are used to maintain numbers stored in radix-64
.Tn ASCII
characters.
This is a notation by which 32-bit integers can be represented by
up to six characters; each character represents a digit in
radix-64 notation.
If the type long contains more than 32 bits, only the low-order
32 bits are used for these operations.
.Pp
The characters used to represent
.Dq digits
are
.Ql .\&
for 0,
.Ql /
for 1,
.Ql 0
-
.Ql 9
for 2 - 11,
.Ql A
-
.Ql Z
for 12 - 37, and
.Ql a
-
.Ql z
for 38 - 63.
.Pp
The
.Fn a64l
function takes a pointer to a radix-64 representation, in which the first
digit is the least significant, and returns a corresponding
.Vt long
value.
If the string pointed to by
.Fa s
contains more than six characters,
.Fn a64l
uses the first six.
If the first six characters of the string contain a null terminator,
.Fn a64l
uses only characters preceding the null terminator.
The
.Fn a64l
function scans the character string from left to right with the least
significant digit on the left, decoding each character as a 6-bit
radix-64 number.
If the type long contains more than 32 bits, the resulting value is
sign-extended.
The behavior of
.Fn a64l
is unspecified if
.Fa s
is a null pointer or the string pointed to by
.Fa s
was not generated by a previous call to
.Fn l64a .
.Pp
The
.Fn l64a
function takes a
.Vt long
argument and returns a pointer to the corresponding
radix-64 representation.
The behavior of
.Fn l64a
is unspecified if value is negative.
.Pp
The value returned by
.Fn l64a
is a pointer into a static buffer.
Subsequent calls to
.Fn l64a
may overwrite the buffer.
.Pp
The
.Fn l64a_r
function performs a conversion identical to that of
.Fn l64a
and stores the resulting representation in the memory area pointed to by
.Fa buffer ,
consuming at most
.Fa buflen
characters including the terminating
.Dv NUL
character.
.Sh RETURN VALUES
On successful completion,
.Fn a64l
returns the
.Vt long
value resulting from conversion of the input string.
If a string pointed to by
.Fa s
is an empty string,
.Fn a64l
returns 0.
.Pp
The
.Fn l64a
function returns a pointer to the radix-64 representation.
If value is 0,
.Fn l64a
returns a pointer to an empty string.
.Sh SEE ALSO
.Xr strtoul 3
.Sh HISTORY
The
.Fn a64l ,
.Fn l64a ,
and
.Fn l64a_r
functions are derived from
.Nx
with modifications.
They appeared in
.Fx 6.1 .
.Sh AUTHORS
The
.Fn a64l ,
.Fn l64a ,
and
.Fn l64a_r
functions
were added to
.Fx
by
.An Tom Rhodes Aq Mt trhodes@FreeBSD.org .
Almost all of this manual page came from the
.Tn POSIX
standard.